Handheld surveying device and method

ABSTRACT

A handheld survey device includes a Global Positioning System (GPS) receiver for receiving position information, a pointer to point to the location to be measured, a measuring device to measure the distance between the handheld device and the location to be measured and a level and heading device to determine the level and heading of the handheld device. The GPS receiver may be a real time kinematic (RTK) GPS receiver and may be augmented by the use of a dead reckoning (DR) positioning unit. A processor located within the handheld device computes the position of the location using the position information provided by the GPS receiver and/or the DR system, the distance measured between the handheld device and the location, and the level and heading information. The position computed meets the stringent accuracy requirements dictated by survey applications without the use of a range pole.

RELATED APPLICATION

This application hereby claims the priority benefit of and is acontinuation-in-part of co-pending application Ser. No. 08/842,699, nowU.S. Pat. No. 5,903,235 entitled "Handheld Surveying Device and Method,filed Apr. 15, 1997, by Mark Edward Nichols, and assigned to theAssignee of the present invention.

FIELD OF THE INVENTION

The present invention relates to surveying using satellite navigationalequipment.

BACKGROUND

The art of surveying and mapping has dramatically changed through theuse of satellite navigation equipment. Satellite survey devices includereceivers that receive position signals from the global positioningsystem (GPS), Global Navigation Satellite System (GLONASS) receiver orother satellite or pseudolite systems. The satellite position signalsare used to compute the position of the receiver.

Survey and GIS (Geographic Information System) applications requireextremely high accuracy positions measurements. Due to selectiveavailability (S/A) and environmental conditions, the position signalsmay be degraded to 100 meter accuracy, which is not satisfactory forSurvey and GIS use. Differential correction (DGPS) and real timekinematic (RTK) processes are therefore used to increase accuracy to thewithin 0.2-5 meter accuracy and centimeter accuracy, respectfully. RTKand real time computation of DGPS both require the use of an additionalradio frequency receiver for reception of additional data that is usedto compute a corrected, more accurate, position. Thus, the satellitesurvey device which is typically called the "rover device", includes arange pole for identifying the point for which a location is to becomputed, a user input/output device for entry and display ofinformation and data, a satellite receiver and a radio receiver.

Examples of satellite survey devices include the GPS Total Station®manufactured by Trimble Navigation Ltd. of Sunnyvale, Calif. (GPS TotalStation is a registered trademark of Trimble Navigation Ltd.). The GPSTotal Station includes a GPS antenna mounted on a range pole. The userplaces the range pole over the location to be measured. A simplifieddrawing of this type of surveying equipment is shown in FIG. 1. Therange pole 10 has attached to it the antenna 20 for receiving GPSsignals and a circular level or vial 30. The user 40 holds the pole 10and moves the pole 10 about until the level 30 indicates that the poleis vertically oriented and the bottom of the pole touches the location50 to be surveyed. Once vertically oriented, the information receivedvia the GPS antenna can be used to accurately compute the position ofthe location 50. Typically, the user will have a backpack 60 thatincludes a wireless link, such as a radio modem 70, for receivingcorrection signals from differential GPS (DGPS) base stations. UsingDGPS technology, more precise measurements are obtained. The backpack 60also contains equipment and circuits for generating positionalinformation based upon the signals received through antenna 20 andwireless link 70. The data collection device 100 enables the user tomake manual entries, and also provides a visual reading of the surveymeasurements obtained.

Handheld GPS receivers presently are available on the consumer market.These devices ally marketed towards the recreational sailor or hiker,provide position information accurate to 20-100 meters. Smaller, lighterGPS receivers with survey accuracy would be desirable to surveyorsbecause of ease of transport in the field.

In order to be of utility, surveying data must provide accuracy withinthe range of 5 mm to 10 or 20 cm. The handheld devices available do notprovide this high level of accuracy needed. Thus, it is desirable toprovide an accurate handheld device to be used in survey and GISapplications.

SUMMARY OF THE INVENTION

The present invention describes a handheld surveying device usingsatellite navigational or similar positioning technology and a deadreckoning (DR) system. The handheld device eliminates the need for arange pole and provides accurate position information. In oneembodiment, the device is embodied in a handheld housing which includesa global positioning system (GPS) receiver; a DR system; a digital leveland heading device for determining the level and heading of the handhelddevice; a pointing device that enables the user to point the handhelddevice to the location to be measured; and a measuring device to measurethe distance between the handheld device and the location to bemeasured. The GPS receiver may be a real time kinematic (RTK) GPSreceiver.

Using the handheld device, the pointing device is used to point to thelocation to be measured. The measuring device measures the differencebetween the location of the measuring device (computed using GPS and/orDR measurements) and the location pointed to that is to be measured. Thedigital level and heading device provides data for correction ofposition information due to the orientation of the handheld device. Byincorporating these elements into a handheld device, the need for arange pole is eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will beapparent to one skilled in the art from the following detaileddescription in which:

FIG. 1 is a simplified prior art drawing of a Global Positioning SystemSurveying Device.

FIG. 2a and FIG. 2b are simplified illustrations of embodiments of thehandheld surveying device of the present invention.

FIG. 3a is a simplified block diagram illustrating one embodiment ofelements of the handheld surveying device of the present invention andFIG. 3b illustrates an alternate embodiment of the handheld surveyingdevice of the present invention.

FIG. 4 is a simplified flow diagram illustrating the processing to beperformed with respect to one embodiment of the handheld device of thepresent invention.

FIG. 5, FIG. 6a, and FIG. 6b are diagrams used to describe oneembodiment of the computations to be performed in one embodiment of thehandheld device of the present invention.

FIG. 7a, FIG. 7b, FIG. 7c and FIG. 8 illustrate another embodiment ofthe computations to be performed in another embodiment of the handhelddevice of the present invention.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousdetails are set forth in order to provide a thorough understanding ofthe present invention. However, it will be apparent to one skilled inthe art that these specific details are not required in order topractice the present invention. In other instances, well-knownelectrical structures and circuits are shown in block diagram form inorder not to obscure the present invention unnecessarily.

The surveying device of the present invention provides a handheld devicethat is easy to use and eliminates a need to use a cumbersome rangepole. A simplified illustration of the handheld device is shown in FIG.2a. Using the handheld device 200, the user 205 can measure a positionof a particular location 10. The handheld device eliminates the need fora range pole (i.e., 10, FIG. 1), or a level (30, FIG. 1) to orient thedevice directly over the location to be measured.

The device 200 includes the circuitry to receive positioning informationfrom the global positioning system (GPS), or similar system, as well asinformation to adjust the positioning information received to compute anaccurate position of the location to be determined 210.

An alternate embodiment is illustrated in FIG. 2b. In this embodiment.certain components are placed in a fanny pack 230 which hooks around theuser's waist with a belt. For example, the radio receiver and a datastorage device may be placed in the fanny pack, freeing up space in thehandheld portion 235 of the device. However, it is preferred that thelaser pointer, GPS antenna and digital level and heading device bemaintained in the handheld device in order that user be able to point tothe location to be measured and acquire accurate position data.

A simplified block diagram of one embodiment of the handheld device isshown in FIG. 3a. The device typically includes input/output elements,such as a display and keypad 305, a processor 310, and relatedcomponents such as memory, controllers and the like, a positioningantenna and receiver 315, a radio receiver 320, digital level andheading element 330, measuring element 340 and pointing element 350.

The input/output display and keypad 305 are used to provide feedback tothe user and enable the user to enter in information, such as notesregarding the survey process performed. Processor 310 performs thecomputations necessary to determine the desired location, and furthercontrols the remaining elements to acquire the data needed to performthese calculations. Processor 310 also performs functions such asstoring data in the memory for subsequent access, and displayingselective information on the display during survey.

The antenna and receiver 315 receive position information with respectto the location of the antenna on the handheld device. In the presentembodiment, equipment compatible with the Global Positioning System(GPS) are used. However, it is readily apparent an antenna and receivercompatible with other types of positioning systems may be employed.Other types of positioning systems include the Global OrbitingNavigation System (GLONASS), long-range navigation (LORAN-C) system,uncoordinated beacon signals, and pseudolite systems.

In addition to these RF-based positioning information systems, thehandheld device may incorporate an internal (or at least associated)dead reckoning (DR) system. 317. DR systems are useful where GPS orother RF positioning signals arc unavailable (e.g., under densecanopies, in urban canyons, etc.). The integration of DR and GPSreceiver systems is well known in the art (see, e.g., U.S. Pat. No.5,538,776, incorporated herein by reference), however, no prior GPS/DRsystem has included the pointing and/or measuring elements describedherein.

Briefly, as explained in U.S. Pat. No. 5,538,776, DR systems compute aposition solution by measuring or deducing displacements from a knownstarting point in accordance with motion of the user. Two types ofwell-known DR systems are inertial navigation systems (INS) and systemsbased on a combination of a compass or rate gyro and a speedometer. INSuse data from three orthogonal accelerometers. Double integrationcalculates position from acceleration as the user moves. Three gyros arealso required to measure the attitude of the accelerometers and removethe effects of gravity. Results of the integration are added to thestarting position to obtain current location. Compass or rategyro/speedometer DR systems determine location with heading and speedindicators and have been automated with microcomputers in vehicularapplications.

The above-cited U.S. Patent introduces a third kind of DR system,primarily directed to individual foot travelers. In general, the systemcombines a digital electronic compass with both a pedometer and abarometric altimeter. Pedometers use a spring-loaded mechanical pendulumto sense walking motions of the user. The pendulum operates a switch sothat the up-down motion of the pendulum may be counted by the unit'selectronics. A scale factor that is proportional to the user's stridelength is then applied to the count to determine the distance traveled.The altimeter provides measures in elevation changes as the usertravels.

The above sensors are used in a complementary configuration with GPS anddigital electronic maps. The integrated GPS-DR navigation systemcontinuously tracks a user's position without references to externalaids or signals. Thus, such a DR device is well suited to the presentinvention, which is preferably embodied in a handheld device.

Once the position information is received (i.e., either with respect tothe antenna of the handheld device where GPS signals are used or fromthe internal or associated DR unit 317), the difference in positionbetween the handheld device and the location to be measured must bedetermined. The digital level and heading device 330 identifies the tilt(angle .O slashed.) and the heading (angle θ) at which the user isholding the handheld device. This provides the data used to determinethe relative position of the handheld device with respect to theposition to be measured. Thus, there is no need for the user to hold thehandheld device in a prespecified orientation directly over the locationto be measured. The device 330 can be embodied as two separate devices,one determining the level of the handheld device, and the otherdetermining the heading. Alternately, the device 330 can be oneintegrated device. One example of a device 330 is the TMCI which isavailable from Precision Navigation Ltd., Sunnyvale, Calif. In somecases, elements of the DR system 317 may be shared with the digitallevel and heading device 330.

The measuring element 340 is used to measure the distance between thehandheld device and the location to be measured. Preferably, themeasuring element 340 is any compact measuring device that functions tonon-obtrusively measure the distance between the handheld device and thelocation to be measured. In addition, it is preferred that the measuringdevice does not require a device, such as a reflective object, to beplaced at the location to be measured. One example of the measuringdevice 340 is a sonic-based measuring system, which sonically determinesthe distance between the measuring device and the location to bemeasured. Another device 340 that can be used is a laser-based measuringdevice that uses the time of flight or performs a phase comparison inorder to measure the distance. Preferably, as noted above, the lasermeasuring device does not require a reflective surface at the locationto be measured. Examples of measuring element products include Criterionby Laser Technology Colorado, and Pulsar by IBEO, Hamburg, Germany.

The pointing element 350 provides feedback to the user to enable theuser to identify the location to be measured. In one embodiment, a laserpointer is used. The laser pointer illuminates a spot on a surface andcan be moved by the user to position the spot at the location to bemeasured. The laser pointer should be concentric with the measuringdevice, or slightly offset. If slightly offset, the difference betweenthe location of the laser pointer within the handheld device and thelocation of the measuring device in the handheld device can bedetermined using known offset and tolerances. Alternately, it maydesirable in certain situations to use an optical plummet. For example,an optical plummet may be desirable in those situations where theambient light is so bright that the location the laser pointer ispointing to cannot be visually determined. The optical plummet isattached to or incorporated into the housing of the device and providesthe user a visual picture of the area that the device is pointing to,and a centering element, such as a cross-hair, to enable the user tovisually determine the location where the handheld device is pointingto. The offset between the optical plummet and the measuring devicewould be a known, predetermined quantity, enabling the measurement to beaccurately determined.

The handheld device 300 may also include a radio receiver for receivingdifferential GPS correction signals for increasing the accuracy of themeasurements. Correction signals are transmitted by a DGPS base station,and received by the radio receiver 320. These correction signals arethen used to adjust the positioning data received through the GPSantenna and receiver 315. Although in the present embodiment, a separateantenna/receiver is used, it is contemplated that one antenna/receivercan be used to receive position signals and correction signals.Furthermore, other elements may be added to the handheld device toprovide additional functionality and features.

Alternatively, in place of a DGPS receiver, an RTK (real time kinematic)GPS receiver may be used. RTK GPS receivers are well-known in the GPSarts and provide up to centimeter-level accuracy. Unlike DGPS receivers,RTK GPS receivers rely on satellite observables transmitted by a radioor other link between the base and mobile receivers, whether or notthere is a clear line of site (e.g., a multiple radio relay link may beused), to ensure that accuracy in the mobile position measurements ismaintained and the survey information is correct. Further detailsregarding RTK methodologies may be found in Talbot et al., U.S. Pat. No.5,519,620, entitled "Centimeter Accurate Global Positioning SystemReceiver for On-The-Fly Real Time Kinematic Measurement and Control",incorporated herein by reference.

FIG. 3b is a simplified block diagram of an alternate embodiment of thehandheld survey device. The device 360 is controlled by systemcontroller and transform calculator 362. Positioning signals arereceived via a GPS antenna 364 and input to GPS Receiver/Processor 366.Preferably the GPS Receiver/Processor performs differential correctionand therefore includes a differential receiver antenna 368 and receiver370; as is readily apparent to one skilled in the art, other forms ofcorrection can be used. For example, an RTK GPS receiver (and itsassociated radios and antennas) may be used in place ofreceiver/processor 366, differential receiver 370 and differentialantenna 368 without departing from the general unit configuration shownin the diagram. Positioning data is transferred to the system controllerand transform calculator 362 by GPS receiver processor 366 and DR unit317. Transforms are applied to the positioning data received based uponthe tilt provided by tilt meter 372, heading, provided by heading meter374 and distance to the point to be measured, provided by distance meter376 as pointed to by laser pointer 378. The transformed positioning datareflects the position of the point pointed to by laser pointer 378.

The system 360 also includes a battery or other power source 380 used topower the device 360, a keyboard 382 to enable the user to input datasuch as notes or the like, and a display 384 to provide the usualfeedback to the user. Data storage 386 is also included for temporaryand semi-permanent storage of data collected and computed in accordancewith the teachings of the present invention.

The process for determining the position of a location using a handhelddevice is described with reference to FIG. 4. At step 405, using thepointing device, the user points the handheld device to the location tobe measured. At step 410, the slope and heading of the handheld deviceis determined. At step 415, the distance between the handheld device andthe location to be measured also is determined. Positioning data, suchas that received through a GPS antenna and receiver and/or DR unit, isacquired. This position data identifies the position of the handhelddevice (e.g., for GPS measurements, the position of the antenna). Atstep 420, the difference in position between the unit (e.g., the phasecenter of the GPS antenna) and the location to be measured isdetermined. This data used includes the tilt and heading of the handhelddevice, the distance between the handheld device and the location to bemeasured, and known offsets between the phase center of the antenna andthe measuring device. Once the difference in position between thehandheld unit and the location to be measured is determined, the GPS/DRdata is adjusted to determine the position of the location. Thus, a usercan easily acquire position measurements without the use of a cumbersomerange pole and circular level.

An example of a measurement to be performed by the handheld device ofthe present invention is described with respect to FIG. 5, FIG. 6a andFIG. 6b. FIG. 5 illustrates an elevational view of a handheld measuringdevice 500, which includes the antenna 505 having phase center 510. Adistance O₁ is used to identify the difference in position between thephase center of the antenna 510 and the measuring center of themeasuring device 515. The measuring device 515 determines the distanceD₁ between the location to be measured 520 and the measuring center ofthe measuring device 515. The antenna 505 receives positioning signalswhich determine the distance or location of the antenna phase center510. The variable .O slashed. 525 corresponds to the tilt angle fromvertical as measured by the inclinometer (not shown) included in thedevice. It should be noted that the inclinometer can be located anywhereon the axis of line O₁ between the antenna phase center 510 and thepointing device 535.

To relate the coordinates of the GPS antenna phase center 510, given inlatitude, longitude and latitude (or any x, y, z coordinate system) tothe coordinates to the point being targeted by the laser pointer, thefollowing coordinate transform is used. Let .O slashed. be the tiltangle of the laser beam in degrees measured from vertical by anappropriate instrument. Let θ be the angle of the laser beam projectedon the local horizontal plane (x, y). For purposes of explanation, alocal coordinate system in x, y, z as shown in FIG. 6a is defined, wherex corresponds to East, y corresponds to North, and altitude correspondsto z. The origin is centered on the laser beam source 515. Thecoordinates of the GPS receiver antenna phase center be called x_(o),y_(o), z_(o). The coordinates of the point 520 to be measured are calledx_(o) ', y_(o) ', z_(o) '. The vector defined by the laser beam islength D₂ (this length includes the beam length D, plus the offset fromphase center to laser O₁). Reference to FIG. 6a, the two points arerelated as follows:

    x.sub.o '=x.sub.o +Δx

    y.sub.o '=y.sub.o +Δy

    z.sub.o '=z.sub.o +Δz

Where by inspection of FIG. 6b:

    •x=D.sub.2 (sin .o slashed.)(sin θ)

    •y=D.sub.2 (sin .o slashed.)(cos θ)

    •z=-D.sub.2 cos .o slashed.

or

    x.sub.o '=x.sub.o +D.sub.2 (sin .o slashed.)(sin θ)

    y.sub.o '=y.sub.o +D.sub.2 (sin .o slashed.)(cos θ)

    z.sub.o '=z.sub.o D.sub.2 cos .o slashed.

An alternate example is illustrated with respect to FIGS. 7a, 7b, 7c and8. In the previous example, the computations performed take into accountmovement of the user's forearm when computing the location of thedesired point to be determined. In the present example, as illustratedin FIG. 7a, the handheld device 105 includes two inclinometers 710, 715oriented perpendicular to one another. These inclinometers may form partof the DR system or may be independent. The two inclinometers 710, 715can be located at any elevation (Δz) independently of one another. Thefirst inclinometer 710 measures the tilt of the device along thelengthwise axis in the yz plane, which corresponds to "elevation". Thesecond inclinometer 715 measures the tilt along the width-wise axis(angle β) in the xz plane which corresponds to "roll". This isillustrated by the diagrams of FIGS. 7b and 7c.

FIG. 8 illustrates the relationships among the various componentsutilized to determine the location to be measured 820 that is pointed toby the pointing device. The origin of the local reference systemcorresponds to the phase center of the GPS antenna.

Using intermediate lengths Dxz-Dyz:

    Δz=Dyz cos α

    Δyz=Dz cos β

    ∴ Δz=D.sub.2 cos α cos β

where Dz is the known distance between the pointing device and the pointto be measured (e.g., laser beam length). Similarly, ##EQU1## and,

    Δy=Dyz sin α

    Dyz=D.sub.2 cos β

    ∴Δy=D.sub.2 sin α cos β

Relative to the phase center, x_(o), y_(o), z_(o) of the antenna, thecoordinates of the point to be measured 820 x_(o) ', y_(o) ', z_(o) 'are determined to be

    x.sub.o '=x.sub.o +Δx

    y.sub.o '=y.sub.o +Δy

    z.sub.o '=z.sub.o +Δz

which equals,

    x.sub.o '=x.sub.o +D.sub.2 cos α sin β

    y.sub.o '=y.sub.o +D.sub.2 sin α cos β

    z.sub.o '=z.sub.o +D.sub.2 cos α cos β

The invention has been described in conjunction with the preferredembodiment. It is evident that numerous alternatives, modifications,variations and uses will be apparent to those skilled in the art inlight of the foregoing description.

What is claimed is:
 1. A handheld device, comprising:a globalpositioning system (GPS) receiver unit configured to provide firstpositioning information signals; a dead reckoning unit configured toprovide second positioning information signals; a pointing element forpointing to a location to be measured; a measuring element for measuringthe distance between the location to be measured and the handhelddevice; a level and heading element that determines a tilt andorientation of the handheld device; a processor coupled to receive thefirst and second positioning information signals, the distance betweenthe location to be measured and the handheld device, and the level andheadings of the handheld device, said processor computing the positionof the location to be measured.
 2. The handheld survey device of claim1, wherein the GPS receiver comprises a real time kinematic (RTK) GPSreceiver.
 3. The handheld survey device of claim 1, wherein the pointingelement is a laser pointer.
 4. The handheld survey device of claim 1,wherein the pointing element is an optical plummet.
 5. The handheldsurvey device of claim 1, wherein the measuring element is a sonic-basedmeasuring device.
 6. The handheld survey device of claim 1, wherein themeasuring element is a laser-based measuring device.
 7. The handheldsurvey device of claim 1, wherein the processor computes the position ofthe location to be measured in real time.
 8. A method for surveying alocation using a handheld device comprising the steps of:positioning thehandheld device to point to the location; determining the level andheading of the handheld device; measuring the distance between thelocation and the handheld device; determining the position of thehandheld device using position signals indicative of the position of thehandheld device, the position signals being global positioning system(GPS) signals and dead reckoning position signals; and computing theposition of the location using the position signals, the measureddistance between the location and the handheld device, and the level andheading of the handheld device.
 9. The method for surveying as set forthin claim 8, wherein determining the position signals using GPS signalscomprises computing the position of the handheld device using a realtime kinematic (RTK) GPS receiver.
 10. The method for surveying as setforth in claim 8, wherein the position of the location is computed inreal time.